In order to overcome redundancy on a network transmission path, a rapid spanning tree protocol (RSTP, see IEEE802.1w) and a multiple spanning tree protocol (MSTP, see IEEE802.1w) are adopted in the current high-availability network. These two protocols are applicable to a ring network to achieve path redundancy through certain algorithms, and to prune the ring network into a loop-free tree network at the same time.
Although link failures may be detected by the two protocols, messages are frequently sent during operation to check the network state. It could regularly cause a relatively long time for failure recovery. As a result, the two protocols could not meet requirements of industrial networks in terms of real-time property.
To meet the requirements of network protocols on the real-time property of industrial networks, International Electrotechnical Commission (IEC) has established an industrial automation high-availability network protocol set-IEC 62439 protocols, wherein IEC 62439-2 MRP (Media Redundancy Protocol) utilizes a master-slave network structure; however, only one definite master node exists in the network and only the master equipment is used for dealing with the failure once it occurs. There is a problem in the network risk concentration. In addition, a redundancy protection on the kernel terminal equipment is not achieved. Moreover, the EC 62439-3 PRP (Parallel Redundancy Protocol) uses two equivalently backbone networks, and a fast failure recovery for terminal equipment is realized using a dual-port redundancy technology, but there is a drawback of detecting well states of the dual ports and it results an increase in the system cost.
To this end, the applicant proposes IEC62439-6 distribution redundancy ring network protocol-DRP (Distribution Redundancy Protocol), reference should be made to Chinese patent CN101252426B for the details of the technology, and the distribution redundancy loop protocol employs a network structure in which master stations take turns. However, since the master stations take turns periodically, such requirements as complex loop operation and high hardware requirement should be met.